Determination of alpha-bisabolol in human blood by micro-HPLC–ion trap MS and head space-GC–MS methods

Alpha-bisabolol is a compound present in some essential oils, widely distributed in several plants, including camomile. Two different methods for analysing an essential oil, such as alpha-bisabolol in human blood are reported: the first uses micro-liquid chromatography–electrospray ionisation-mass spectrometry (μHPLC–ESI-MS), whereas the second is based on “head space” injection coupled to gas chromatography–mass spectrometry (HS-GC–MS). For LC–ESI-MS, human blood samples, spiked with alpha-bisabolol, were extracted with hexane and evaporated to dryness under air stream. The residue was then reconstituted with methanol and injected into a C18 column, connected to an ion trap mass spectrometer equipped with an ESI source. Spectra were recorded in the positive ion, selected ion monitoring mode. The detection limit of alpha-bisabolol in blood was 0.125 μmol/l. The preparation of samples for the analysis in HS-GC–MS was limited to blood dilution with water (0.5 ml blood + 1 ml water). Head space vials were heated at 125 °C for 1 h before automatic injection. The HS-GC–MS detection limit (0.13 μmol/l) was similar to that achieved with the μHPLC–ESI-MS method. Successful tests were performed to verify if alpha-bisabolol could be directly measured by the HS-GC–MS method in different biological samples (blood, urine, faeces, homogenate tissues) from rats treated with the camomile essential oil.